
AS3932
Datasheet - D e t a i l e d D e s c r i p t i o n
Table 22. Preamble Requirements in Standard Mode, Scanning Mode and ON/OFF Mode
Bit rate (bit/s)
1560
1488
1424
1364
1310
1260
1212
1170
1128
1092
1056
1024
Maximum duration of the carrier burst in Standard
Mode and Scanning Mode (ms)
10.25
10.75
11.23
11.73
12.21
12.69
13.20
13.67
14.18
14.65
15.15
15.62
Maximum duration of the carrier burst in ON/OFF Mode
(ms)
10.25
10.75
11.23
11.73
12.21
12.69
13.20
13.67
14.18
14.65
15.15
15.62
8.7 False Wake-up Register
The wake-up strategy in the AS3932 is based on 2 steps:
1. Frequency Detection: in this phase the frequency of the received signal is checked.
2. Pattern Correlation: here the pattern is demodulated and checked whether it corresponds to the valid one.
If there is a disturber or noise capable to overcome the first step (frequency detection) without producing a valid pattern, then a false wake-up call
happens.Each time this event is recognized a counter is incremented by one and the respective counter value is stored in a memory cell (false
wake-up register). Thus, the microcontroller can periodically look at the false wake-up register, to get a feeling how noisy the surrounding
environment is and can then react accordingly (e.g. reducing the gain of the LNA during frequency detection, set the AS3932 temporarily to
power down etc.), as shown in the Figure 20 . The false wake-up counter is a useful tool to quickly adapt the system to any changes in the noise
environment and thus avoid false wake-up events.
Most wake-up receivers have to deal with environments that can rapidly change. By periodically monitoring the number of false wake-up events
it is possible to adapt the system setup to the actual characteristics of the environment and enables a better use of the full flexibility of AS3932.
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